Magnetizable image transfer medium



e. M. SUTHEIM ETAL 3,029,157

MAGNETIZABLE IMAGE TRANSFER MEDIUM Filed Nov. 18, 1958 April 10, 1962MAGNETICALLY INERT BACKING SHEET INVENTORS GEORGE M. SUTHEIM HAROLD J.SOUTHCOMB 73, 14..., M, m /fl ATTORNEYS 3,iiZ9,l57 Patented Apr. 10,1962 hce 3,029,157 MAGNETIZABLE WAGE TRANSFER MEDIUM George M. Sutheimand Harold J. Southcomb, Stamford, Conn., assignors to Audio Devices,Inc., New York, N.Y., a corporation of New York Filed Nov. 18, 1958,Ser. No. 774,581 2 Claims. (Cl. 11736.1)

This invention relates to magnetic coatings and, more particularly, to acoating composition adapted to form a magnetizable image transfermedium.

Physical image transfer media such as carbon paper, typewriter ribbonsfor single image transfer and duplicator stencils are commonly used totransfer a visual image from one medium to another. Each of thesetransfer edia comprises a supporting base of paper or plastic foilcarrying a coating of a pigmented or dyed wax-containing material.Inasmuch as relatively little pigment or dye is required for this typeof coating, the physical properties of wax are retained. Thus, thecoating composition can be liquefied for application to the supportingbase simply by melting the wax component of the composition, and afterthe composition solidifies it exhibits the characteristics of the wax,notably its softness, weak cohesive forces, freedom from tackiness andabsence of cold flow, which make it particularly suitable for mechanicaltransfer of a visual image from one medium to another.

For the mechanical transfer of a magnetizable image from one medium toanother, the strength of the magnetic response is directly proportionalto the concentration of the magnetizable material in the composition.Accordingly, a relatively large percentage of magnetizable material mustbe incorporated in a magnetizable image transfer coating composition.Hot-melt compounds such as the waxes used for the aforementioned visualimage transfer coating composition lose their desirable characteristicswhen such relatively large proportions of a magnetizable pigment areadded to the waxes. Other conventional materials which are generallyusefulin forming thin films, such as the resins and many plasticssoluble at room temperature in technical solvents, are either too hardwhen dried or become tacky when softened by the addition of aplasticizer. Greases, on the other hand, are prone to cold flow eventhough the grease is relatively hard. The problem, then, is to produce amagnctizable image transfer coating composition which can bemechanically transferred from one medium to the other with the ease andclarity of detail characteristic of the visual image transfer coatingcompositions.

We have now discovered that it is possible to compound a mixture offinely-divided magnetizable material with a minor proportion of certainother materials with the result that the mixture exhibits theaforementioned desired magnetic and physical characteristics for amagnetizable image transfer coating composition. The composition of ourinvention consists essentially of (a) a grease-like material of thegroup consisting of soft mineral waxes, animal fats and vegetable fats,(b) a bodying agent of the group consisting of fatty acids having from12 to 18 carbon atoms and the esters and metallic salts thereof, (c) ahydrophobic oil soluble normally-solid chain polymer, (d) an amount of afinely-divided magnetizable material at least equal to the total amountof the aforementioned materials, and (e) an organic solvent capable ofsolvating the normally-solid polymer and present in amount sufficient toimpart a fluid consistency to the composition. The composition can bereadily applied to a sheet of magnetically inert material to form, afterthe solvent has been driven off, a magnetizable image transfer mediumwhich can be transferred mechanically from one medium to another likethe aforementioned conventional visual image transfer mediums.

In the accompanying drawing, the single FIGURE is a fragmentarycross-sectional view of a magnetisable image transfer medium embodyingthe invention.

The grease-like materials that form the base of our new compositioncomprise soft mineral waxes such as petro latum and microcrystallinepetroleum waxes, as well as animal and vegetable fats such as lanolinand cacao butter. These materials, whether used singly or in combination with one another, are supplemented by other materials, hereinreferred to as bodying agents, which add body to the grease-likematerials. The bodying agents consist of fatty acids having from 12 to18 carbon atoms and the esters and metallic salts thereof. Stearic acid,sorbitan monopalmitate, calcium stearate and barium stearate arerepresentative examples of such bodying agents.

The bodied grease-like material is further reinforced by the addition ofa minor proportion of a hydrophobic, oil-soluble, normally-solidchain-type polymer which is also soluble in a mutual solvent for thebodied greaselike material. Chlorinated rubber, cellulose esters,cellulose ethers and similar polymer compounds are efiective for thispurpose. In the case of relatively inflexible polymers, such as thechlorinated rubber polymers, a plasticizer for the polymer may also beincorporated in the mixture. Dioctyl phthalate or dihexyl phthalate areparticularly suitable, although other plasticizers such as dioctyladipate or dioctyl sebacate are equally efiective.

The resulting mixture is solvated by any suitable solvent such astoluene. Although the solvent may be added directly to the mixture ofgrease-like material, bodying agent and polymer reinforcing agent, wehave found that dissolution of all components is facilitated if thepolymer is first dissolved in a portion of the solvent and the resultingpolymer solution is then added to the other solid components along withthe balance of the solvent.

The resulting mixture forms the carrier vehicle for the magnetizablematerial. The magnetizable material may comprise any of thefinely-divided materials corn monly used as the magnetizable componentof magnetic recording tapes and sheets, such, for example, asferrosoferric oxide and gamma ferric oxide. Finely-divided metalliciron, iron alloys and magnetic ferrites are similarly useful.

The proportions of the aforementioned components of the composition ofour invention are such that the amount of the bodying agent is at leastone-half and preferably exceeds that of the grease-like material, thatthe amount of the polymer does not exceed and is generally less than thegrease-like material, and that the amount of the solvent is suificientto impart flowability when these components are admixed with an amountof magnetizable material at least equal to the total amount of thenonvolatile components, to wit, the grease-like material, the bodyingagent and the polymer. Percentagewise, the amount of the bodying agentvaries between 50% and 300% by weight of the grease-like material, theamount of the polymer varies between 20% to by weight of the grease-likematerial, the amount of the solvent varies between 200% and 350% byweight of the total amount of the grease-like material, the bodyingagent and the polymer, and the amount of the magnetizable materialranges between 100% and 200% by weight of the aforesaid total of thegrease-like material, the bodying agent and the polymer.

The resulting composition is then applied by any conventional coatingtechnique, such as by a doctor blade, to a sheet of magnetically inertmaterial such as webs of paper, cellulose acetate, polyvinyl chlorideand acetate polymers and co-polymers thereof, and a polyester such asthe condensation product of ethylene glycol and terephthalic acid. Thecoating is advantageously about 0.25 mil thick, although thinner andthicker coatings are useful. The coated web is then cut into ribbons ofany desired width by means of conventional slitting machinery.

The following specific examples are illustrative of the novelcomposition of our invention. In each example, the components which formthe carrier vehicle for the magnetizable material were simply physicallyadmixed and then the magnetizable material was added. The resultingmixture was then ground in a ball mill or the. like to insure thoroughdispersion of the magnetizable material throughout the vehicle:

Example I Component Identity Parts by Weight Grease-like materialAnhydrous lano1in. 15 Bodying agent Barium stearate 30 PolymerChlorinated rubber l Polymer plastieizer Dioctyl pl1thalate. 15 SolventToluene 150 Magnetizable material Ferrosoferric oxide- 100 Example 11Component Identity Parts by Weight Grease-like material Petzolatum 25Bodying agent t Stearic acid 25 PolymeL Ethyl cellulose Solvent Toluene150 Magnetizable material Ferrosoferric oxide- 100 Example 111 ComponentIdentity Parts by Weight Grease-like material Anhydrous lanolin. 35Bodying agent Sorbitan 25 monopalmltate.

Polymer Ethyl cellulose 10 S0lvent Toluene 200 Magnetizable materialFerrosoferric oxide. 100

Each of the products of Examples I, II and III was applied to a ribbonof cellulose acetate 0.5 mil thick, the thickness of the coating afterdrying being about 0.25 mil. The ribbons were tested by using them. astypewriter ribbons and were eifective in providing magnetizable typedletters and numeralson paper of a clarity equal to that of aconventional typewriter ribbon.

We claim:

1. A coating composition adapted when applied to a sheet of magneticallyinert material to form a magnetizable image transfer medium, thecomposition being characterized by a proportion of magnetizable materialat least equal in weight to the total of the other solid materials inthe composition and consisting essentially of (a) a grease-like materialselected from the group consisting of soft mineral waxes, animal fatsand vegetable fats, (b) from 50 to 300 percent of a bodying agentselected from the group consisting of fatty acids having from 12 to 18carbon atoms and the esters and metallic salts thereof, (c)'from 20 topercent of a hydrophobic, oilsoluble, normally-solid polymer selectedfrom the group consisting of chlorinated rubber, cellulose esters andcellulose ethers, (d) from 200 to 350 percent of a volatile organicsolvent capable of solvating the aforementioned materials, and (e) from100 to 200 percent of a finelydivided magnetizable material selectedfrom the group consisting of ferrosoferric oxide, gamma ferric oxide,metallic iron, iron alloys and ferrites, each of the percentages of thebodying agent and of the hydrophobic polymer being based on theweight ofthe grease-like material While each of the percentages of the organicsolvent and of the magnetizable material are based on the totalamountrof the aforementioned grease-like, bodying and hydrophobicmaterials.

2. A magnetizable image transfer medium comprising a backing sheet ofmagnetically inert material having a coating on one surface thereofconsisting essentially of a major proportion of finely-dividedmagnetizable material selected from the group consisting offerrosoferric oxide, gamma ferric oxide, metallic iron, iron alloysandferrites dispersed in and carried by a composition consistingessentially of (a) a softening agent selected fromv the group consistingof soft mineral waxes, animal fats and vegetable fats, (b) from 50 to300 percent of a bodying agent selected from the group consisting offatty acids having from 12 to 18 carbon atoms and the esters andmetallic salts thereof, and (c) from 20 to 100 percent of a hydrophobic,oil-soluble, normally-solid polymer selected from the group consistingof chlorinated rubber, cellulose esters and cellulose ethers, eachpercentage being based on the weight of the grease-like material, theamount of the finely-divided magnetizable material contained in thecoating being from 100 to 200 percent by weight of the composition.

References Cited in the file of this patent UNITED STATES PATENTS

2. A MAGNETIZABLE IMAGE TRANSFER MEDIUM COMPRISING A BACKING SHEET OFMAGNETICALLY INERT MATERIAL HAVING A COATING ON ONE SURFACE THEREOFCONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF FINELY-DIVIDEDMAGNETIZABLE MATERIAL SELETED FROM THE GROUP CONSISTING OF FERROSOFERRICOXIDE, GAMMA FERRIC OXIDE, METALLIC IRON, IRON ALLOYS AND FERRITESDISPERSED IN AND CARRIED BY A COMPOSITION CNSISTING ESSENTIALLY OF (A) ASOFTENING AGENT SELECTED FROM THE GROUP CONSISTING OF SOFT MINERALWAXES, ANIMAL FATS AND VEGETABLE FATS, (B) FROM 50 TO 300 PERCENT OF ABODYING AGENT SELECTED FROM THE GROUP CONSISTING OF FATTY ACIDS HAVINGFROM 12 TO 18 CARBON ATOMS AND THE ESTERS AND METALLIC SALTS THEREOF,AND (C) FROM 20 TO 100 PERCENT OF A HYDROPHOBIC, OIL-SOLUBLE,NORMALLY-SOLID POLYMER SELECTED FROM THE GROUP CONSISTING OF CHLORINATEDRUBBER, CELLULOSE ESTERS AND CELLULOSE ETHERS, EACH PERCENTAGE BEINGBASED ON THE WEIGHT OF THE GREASE-LIKE MATERIAL, THE AMOUNT OF THEFINELY-DIVIDED MAGNETIZABLE MATERIAL CONTAINED IN THE COATING BEING FROM100 TO 200 PERCENT BY WEIGHT OF THE COMPOSITION.